Purpose: :
The purpose of this study was to determine the reason for thedown-regulation of β-actin gene in the stroma of humankeratoconus compared to normal corneas.

Methods: :
Three normal corneas (ages: 30 to 55 years) and three keratoconuscorneas (ages: 30 to 55 years) were used for RNA isolation fromepithelium and stroma. The β-actin gene was amplified usingAccess RT PCR system. The primers were designed using Primer3for β-actin, human antigen R (HUR), and Glyceraldehyde3-phosphate dehydrogenase (GAPDH). The PCR products were analyzedusing agarose gel electrophoresis. The RNA extracted from stromaof both normal and keratoconus corneas were reverse transcribedto cDNA for quantitative real-time PCR using Bio-Rad IQ5 realtime thermocycler with SyBr Green.

Results: :
The expression of β-actin gene was down-regulated in thestroma of the three keratoconus corneas but not in the stromaof normal and Fuch’s dystrophic corneas. The real-timePCR analysis of HuR gene showed a 6-fold difference in its expressionin keratoconus corneas, which also exhibited decreased expressionof β-actin gene. The GAPDH gene expression was used asan internal standard in all the above analyses, which remainedat the same levels in the stroma of normal and keratoconus corneas.

Conclusions: :
It is known that β-actin mRNA has long half life and HuRbinding to U-rich element is involved in its mRNA stability.Therefore based on the above results, down-regulation of β-actingene during keratoconus could be due to a decrease in HuR proteinexpression.